5 Notes on individual objects

5.1 Stars

RX J0222.5+5033 = BD+49 646: BD+49 646 was also detected by the ROSAT WFC (2RE J0222+503, Pye et al. 1995). The star GSC0330200570 located NE from BD+49 646 is a late A type star unrelated to the X-ray source.
RX J0621.2+4415 = G 101-35: The BRASS error circle now encompasses the Me star. The star has high proper motion.
RX J0635.9+0755 = GSC0073302098: The candidate star GSC0073302098 lacks the strong Ca II H&K emission which would be expected based on the PSPC count rate. However, the a priori probability of coincidence of the ROSAT source with the late G-K $V \approx$ 10.7 star is small enough (5 10^-3) so that the identification can be considered. The ROSAT source is identified with 2E 0633.2+075.
RX J0702.0+1257 = GSC0075701608: Using EUVE data, Vennes et al. (1997) identify the source as a K0IV-V and a hot white dwarf in a wide binary. Part of the softness of the PSPC spectrum could be indeed explained by a contribution from the degenerate star. The XRT source is identical with EUVE J0702+129 and 2RE J0702+125 (Pye et al. 1995).
RX J0704.5-0612 = GSC0482603053 ??: The brightest object in the RGPS error circle is GSC0482603053. A medium resolution spectrum of the star reveals Ca II H&K emission and some evidence for weak H$\alpha$ emission. Unfortunately, no absolute CaII flux could be measured for this active corona, leaving some doubt on the compatibility of the chromospheric signature with the ROSAT X-ray flux. The second brightest object located SW from GSC0482603053 is a late type star without marked activity.
RX J0713.1-0511 = GSC0482302265: The XRT source is identical to 2RE J0713-051.
RX J0721.3-5720 = GSC0855901016 + comp: The candidate M5e star exhibits strong Balmer emission and is probably responsible for a large part of the X-ray emission. The close and comparatively bright star ($V \approx$ 11) GSC0855901016 is a main sequence K0 star. Unfortunately, we do not have Ca II H&K spectra which would have given indication on the level of stellar activity. The a priori coincidence of position between GSC0855901016 and a ROSAT survey source is small (8.2 10^-3) and could indicate that the bright star also contributes to the X-ray emission and constitutes a physical pair with the Me star.
RX J0811.1-5555 = GSC0857001980: The absence of a spectrum covering the Ca II H& K region does not allow to firmly identify this source. However, in this case, the BRASS position which has a better accuracy than the RGPS determination, is centered on GSC0857001980 and excludes any other object than the V $\approx$ 12 late G star. This positional evidence (a priori probability of coincidence of 1.3 10^-2) and the soft X-ray hardness ratios suggest that GSC0857001980 is the counterpart of the ROSAT source.
RX J0828.5-5138 = GSC0816200330: The BRASS position is now centered on the G star GSC0816200330. The low (6 10^-3) a priori probability of a random positional coincidence of the X-ray source with the relatively bright ($V \approx$ 11) star and the soft X-ray hardness ratio suggest a coronal identification.
RX J0845.7-3544 = GSC0714900583: GSC0714900583 is a late G star, which considering the coincidence in position with the X-ray source (8.3 10^-3) and the soft X-ray spectrum is most probably the optical counterpart of the X-ray source.
RX J0856.4-2241 = GSC0658500334: Weak Balmer emission may be present in the spectrum of GSC0658500334. The BRASS position is also centered on the early M star with a similar error radius. The soft X-ray spectrum is also consistent with a coronal identification.
RX J1704.3-4020 = HD 322763: A follow-up HRI observation gives an improved position, RA = 17 04 17.68, DEC = -40 19 47.6 centered on the A star. X-ray emission may originate from an undetected late type companion star.
RX J2010.5+0632 = GSC0050701588: The Me star is probably identified with the Parkes-MIT-NRAO survey source PMN J2010+0632 (Griffith et al. 1995). An X-ray flare was detected during the survey.
RX J2014.8+4501 = HD 192785: The K0V star HD 192785 exhibits H$\alpha$ re-emission (not shown) and was also detected in the Einstein Slew Survey (Schachter et al. 1996).

5.2 Active galactic nuclei

AGN identified in the low galactic latitude regions have all low redshifts and the dominant population is Seyfert 1.

RX J0222.1+5221 = PMM1350-02324516: This identification was already reported in Motch et al. (1991b).
RX J0254.6+3931 = CJ2 0251+393: We did not obtain spectroscopic observation of this quasar. Its identification is reported in Vigotti et al. (1989).
RX J0324.7+3410 = GSC0234901904: This Seyfert 1 nucleus was independently discovered and identified with the HEAO-1 source H0321+340 by Remillard et al. (1993) and with the ROSAT source by Kock et al. (1996).
RX J0452.0+4932 = H0432052: This object was already listed by Hauschildt (1987).
RX J1931.1+0937 = A: Follow up ROSAT HRI observations revealed flare like activity by a factor of $\approx$2 on a time scale of one day. The best HRI position is RA = 19 31 09.23, DEC = +09 37 18.96 with a conservative error radius of 10$^{\prime\prime}$. The proposed optical counterpart displays a blue featureless continuum and is located within the 1$^{\prime\prime}$ radius error circle of the radio source NVSS J193109+093717. Based on these evidences we propose an identification with a BL Lac type of AGN.
RX J2040.3+1059 = PMM0975-19711620: The AGN could be in an interacting system

5.3 Accreting sources

Detailed X-ray and, optical photometric and spectroscopic studies of the new CVs will be presented in future papers.

RX J0649.8-0737 = PMM0750-02887019: This CV is a polar with a $\approx$4.4h orbital period.
RX J0749.1-0549 = PMM0825-05603282: This CV is a polar with a $\approx$3.6h orbital period.
RX J1739.4-2942 = A: RX J1739.5-2942 is probably identical with GRS 1736-297 since the ROSAT position is located well within the 90$^{\prime\prime}$ radius of the 90% confidence circle of GRS 1736-197. The Be/X-ray nature of the source is consistent with the hard ART-P X-ray spectrum observed by GRANAT (Pavlinsky et al. 1994).

5.4 Miscellaneous and optically unidentified

RX J0035.8+5950 = ??: None of the two GSC stars GSC0366601407 (A) and GSC0366600907 (B) lying at the edge of the ROSAT error circle exhibits detectable chromospheric activity.
RX J0529.0+0934 = ??: Objects A and B display featureless continuum. B is bluer than A.
RX J0602.2+2837 = ??: Object A has a featureless continuum. Object B could exhibit H$\alpha$ emission.
RX J0620.6+2644 = ??: The BRASS 90% confidence error area (small circle) does not overlap with the RGPS 90% error area. Because of the improved reduction process, the BRASS position should be considered as the best one. All objects A-E are late type stars without Balmer emission. A: late K, B: G-K, C: K, D: G-K and E: late G.
RX J0621.7+1747 = ??: Object A is a late B type star, B a K type star and C a G-K type star.
RX J0648.7+1516 = ??: The ROSAT source is identical to 1H 0646+152. A short exposure time spectrum of object A reveals a rather blue featureless continuum. B and C are probably late type stars. The finding chart shows the BRASS position as no reliable error radius was returned by the SASS-I process for this source.
RX J0717.4-1119 = ??: The source was not recovered in a subsequent HRI pointing. Object A is a K type star and B has an A spectral type.
RX J0759.1+0748 = ??: Bright X-ray source. Object A has a F-G spectral type and star C displays H$\alpha$ and H${\beta}$ in absorption. Objects D and C are probably extended and do not exhibit strong emission lines up to 6800 Å.
RX J0819.2-0756 = ??: Objects A and B are F-G type stars. Object C is the only object visible inside the HRI error circle (not shown).
RX J1718.4-4029 = ??: The image shown here is a 5 min I band CCD exposure obtained in April 1992 with EFOSC2 on ESO-MPI 2.2 m. The HRI error circle (RA = 17 18 24.13, DEC = -40 29 30.4, 90% confidence radius = 15.7$^{\prime\prime}$) is plotted. Objects A, B and C display H$\alpha$ and H${\beta}$ absorption lines.
RX J1740.7-2818 = ??: The CCD image shown here is a 5 min I band exposure obtained with EFOSC2 and the MPI-ESO 2.2 m telescope in April 1992. The field is heavily reddened. Objects A, B, C and D are late M stars without any noticeable Balmer emission.
RX J1742.3-2737 = ??: The CCD image shown here is a 2 min I band exposure obtained with EFOSC2 and the MPI-ESO 2.2 m telescope in April 1992. The field is heavily reddened. Object A is a reddened A-F type star and object B a reddened G-K star.
RX J1749.8-3312 = SLX 1746-331: The CCD image shown here is a 5 min I band exposure obtained with EFOSC2 and the MPI-ESO 2.2 m telescope in April 1992. The field is heavily reddened. Object A is a G-K type star.
RX J1749.8-3312 = 1RXS J174948.4-331215 is probably identified with the soft transient SLX 1746-331 (Skinner et al. 1990). The source was discovered by the Spacelab-2 coded-mask X-ray telescope in July-August 1985. Based on its ultrasoft spectrum and transient nature White & van Paradijs (1996) classify the source as a black hole transient. During the ROSAT survey observation (1990 Sep. 08.97 to 1990 Sep. 10.30) the source was caught in outburst and not detected during a subsequent ROSAT HRI follow-up observation (1994 Oct. 02.25 - 02.27). Considering the expected low mass of the companion star and high interstellar absorption on the line of sight, the optical identification is likely to be difficult outside X-ray outbursts.
RX J1804.1+0042 = PMM0900-11515260: Follow-up ROSAT HRI observations show the source to be extended. Its mean position is RA = 18 04 08.6, DEC = +00 42 26.3, well centered on an extended optical object which could be an elliptical galaxy. A low S/N spectrum suggests a possible redshift of z = 0.07 $\pm$ 0.02. The galaxy is probably identified with the Parkes-MIT-NRAO radio source PMN J1804+0042 (Brinkmann et al. 1997).
RX J1936.3+2632 = A: = 2EUVE J1936+26.5
RX J1943.9+2118 = ??: We show a 10 min I band CCD exposure obtained in September 1995 with the 1.2m telescope at OHP. The large error circle represents the RGPS localisation whereas the small one is derived from a follow-up ROSAT HRI observation. The HRI position is RA = 19 43 56.16, DEC = +21 18 24.8 with a conservative error circle of 10$^{\prime\prime}$. A is a reddened object without marked features apart from the Na I line and a possible Mg G band hollow. The position of A, RA = 19 43 56.2, DEC = +21 18 20.4 is outside the error circle of the radio source NVSS J194356+211826 which is itself close to the centre of the HRI error circle. The overall radio, optical and X-ray picture favours a heavily absorbed extragalactic identification.
RX J1950.0+3821 = ??: Objects A, B, C and D are G type stars. The RGPS error circle contains a radio source NVSS J195004+382210 which is located $\approx$ 8$^{\prime\prime}$ north of A.
RX J2102.0+3359 = ?? UV excess object: We show here the BRASS position overlayed on a 10 min B filter CCD image obtained with the OHP 1.2m telescope in September 1995. Object A is a late G early K star, B a G star. A low S/N spectrum reveals a featureless continuum for object C. Object X, located at RA = 21 02 01.4, DEC = +33 59 29.6 exhibits a strong UV excess with B = 21.6 and U-B = -1.1 $\pm$ 0.3. The softness of the X-ray source and the presence of an UV excess object in the ROSAT error circle argue in favour of an AM Her system. Final identification should however await spectroscopic observations.
RX J2104.2+2118 = ??: Objects A and B are late type stars. Object E displays a blue featureless continuum. The radio source NVSSJ210415+211805, is located in the RGPS and BRASS error circles, $\approx$ 2$^{\prime\prime}$ southern of object F.
RX J2156.3+3318 = PMM1200-18997159: X-ray emission is slightly extended by 1 arcmin and centered on the presumably elliptical galaxy PMM1200-18997159 (z = 0.079, B=16.2, R=12.4). The $F_{\rm X}$/$F_{\rm opt}$ ratio is compatible with normal emission from the galaxy without the need to add cluster contribution. The radio source NVSS J215623+331837 is coincident with the galaxy.

Note added in proof: While the paper was under revision we obtained new observations of the field of RXJ0759+0748 revealing that object D is an AGN at z $\approx$ 0.15.

Acknowledgements

We thank the night assistants at Observatoire de Haute-Provence for carrying out some of the observations at the 1.2m telescope. We are grateful to the referee for many helpful comments and suggestions. The ROSAT project is supported by the Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF/DLR) and the Max-Planck-Gesellschaft. C.M. acknowledges support from a CNRS-MPG cooperation contract and thanks Prof. J. Trümper and the ROSAT group for their hospitality and fruitful discussions. We are particularly grateful to the MPE team for providing early access to RASS data. This research has made use of the ALADIN sky atlas and of the SIMBAD database operated at CDS, Strasbourg, France. We thank F. Ochsenbein for providing easy access to the GSC and to the USNO-A1.0 catalogues. Finding charts were extracted from the Digitized Sky Survey, produced at the Space Telescope Science Institute (ST ScI) under U.S. Government grant NAG W-2166.