Companion Object Research Articles

The Gravitational Lens System B1030+074. Discovery and Follow-up

We report the discovery of a new double image gravitational lens system B1030+074 which was found during the Jodrell Bank - VLA Astrometric Survey (JVAS). We have collected extensive radio data on the system using the VLA, MERLIN, the EVN and the VLBA as well as HST WFPC2 and NICMOS observations. The lensed images are separated by 1.56 arcseconds and their flux density ratio at centimetric wavelengths is approximately 14:1 although the ratio is slightly frequency dependent and the images appear to be time variable. The HST pictures show both the lensed images and the lensing galaxy close to the weaker image. The lensing galaxy has substructure which could be either part of the galaxy or a companion object. We have modeled B1030+074 using a Singular Isothermal Ellipsoid that yielded a time delay of 156/h50 days. This lens is likely to be suitable for the measurement of the Hubble constant.

HI Study of the NGC 6744 System

AbstractWe present the preliminary results of our 5-configuration, 20-pointing mosaic with the Australia Telescope Compact Array of the neutral hydrogen in the nearby spiral galaxy NGC 6744. The bulk of the HI resides in a ‘ring’ underlying the outer optical disk, with 2 HI spiral arms extending further out to almost 1·5 optical radii. The velocity field is fairly regular, apart from evidence for streaming motions along the HI arms, and the influence of the companion IB(s)m galaxy NGC 6744A. We associate a cloud of HI at a heliocentric velocity of 846 km s−1 with another companion object, ESO 104–g44. Our attempts to construct a mass model for NGC 6744 suffer from poor resolution in the inner disk, and the uncertainty in the total HI flux of NGC 6744. We anticipate that HIPASS observations will be crucial in resolving the latter issue.

The Quest for a Supernova Companion

Pilar Ruiz-Lapuente Some stars end their lives in supernova explosions as they accrete matter from a companion object. At some point, a critical mass is reached, the Chandrasekhar mass, and the star becomes a fusion bomb. But observational evidence about the companion stars in supernovae is lacking. In her Perspective, Ruiz-Lapuente discusses recent efforts to understand how mass is transferred to stars before a supernova explosion and how the nature of the companion object might be revealed.

Spectroscopy of Close Companions to Quasi-stellar Objects and the Ages of Interaction-induced Starbursts

We present low-resolution absorption-line spectra of three candidate close (<3'') companions to the low-redshift QSOs 3CR 323.1, PG 1700+518, and PKS 2135-147. The spectra were obtained with the Low-Resolution Imaging Spectrometer (LRIS) on the Keck telescopes and with the Faint Object Spectrograph on the University of Hawaii 2.2 m telescope. For 3CR 323.1 and PG 1700+518, we measure relative velocities that are consistent with an association between the QSOs and their companion galaxies. The spectral features of the companion galaxy to 3CR 323.1 indicate a stellar population of intermediate age (~2.3 Gyr). In contrast, the spectrum of the companion object to PG 1700+518 shows strong Balmer absorption lines from a relatively young stellar population, along with the Mg I b absorption feature and the 4000 A break from an older population. By modeling the two stellar components of this spectrum, it is possible to estimate the time that has elapsed since the end of the most recent major starburst event: we obtain approximately 0.1 Gyr. This event may have coincided with an interaction that triggered the QSO activity. Finally, our spectroscopy shows conclusively that the supposed companion to PKS 2135-147 is actually a projected Galactic G star.

AO 0235 + 164 and Surrounding Field: Surprising HST Results

view Abstract Citations (42) References (27) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS AO 0235 + 164 and Surrounding Field: Surprising HST Results Burbidge, E. M. ; Beaver, E. A. ; Cohen, Ross D. ; Junkkarinen, V. T. ; Lyons, R. W. Abstract Results obtained with the Hubble Space Telescope on the highly variable radio, x-ray, and γ-ray emitting QSO (or BL Lac object) AO 0235+164 are presented and analyzed. WFPC2 images were obtained in 1994 June, when AO 0235+164 was bright (m ~ 17), and the results are described in Sec. 3. After subtraction of the PSF of the QSO, hereafter called AO following the nomenclature of Yanny et al. (1989), the companion object named A, 2" south of AO, is discovered not to be an elliptical galaxy as hypothesized earlier, but to be an AGN object, with a central UV-bright point-source nucleus and faint surrounding nebulosity extending to AO. The second companion object 1.3" east of AO discovered by Yanny et al. (1989) and named object A1, appears more like a normal spiral galaxy. We have measured the positions, luminosities, and colors of some 30 faint objects in the field around AO 0235+164; most are extended and may be star- forming galaxies in a loose group or cluster. Our most surprising result of the HST observations comes from FOS spectra obtained in 1995 July, discussed in Sec. 4. Because of a positioning error of the telescope and AO's faintness at that time (m20), object A was observed instead of the intended target AO. Serendipitously, we discovered A to have broad deep BALQSO-type absorptions of C IV, Si IV, H V shortward of broad emissions. A is thus ejecting high velocity, highly ionized gas into the surrounding IGM. We discuss in Sec. 5 the relationship of the objects in the central 10" x 10" region around AO, where redshifts z_e_ = 0.94, z_a_ = 0.524, 0.851 in AO, z_e_ = 0.524 and z_BAL_ = 0.511 in A, are found. We hypothesize that some of the 30 faint objects in the 77" x 77" field may be part of a large star-forming region at z ~ 0.5, as suggested for a few objects by Yanny et al. (1989). The proximity of two highly active extragalactic objects, AO 0235 + 164 and its AGN companion A, is remarkable and one of the authors (EMB) suggests it may require consideration of a non-cosmological component of redshift in AO 0235+164. Publication: The Astronomical Journal Pub Date: December 1996 DOI: 10.1086/118199 Bibcode: 1996AJ....112.2533B Keywords: QUASARS: INDIVIDUAL: AO 0235+164; GALAXIES: ACTIVE; QUASARS: ABSORPTION LINES full text sources ADS | data products SIMBAD (31) NED (31) MAST (1) ESA (1)

An H i/Optical Atlas of H II Galaxies and Their Companions: Erratum

view Abstract Citations (36) References (1) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An H i/Optical Atlas of H II Galaxies and Their Companions: Erratum Taylor, Christopher L. ; Brinks, Elias ; Grashuis, Randy M. ; Skillman, Evan D. Abstract In the paper "An H I/Optical Atlas of H II Galaxies and Their Companions" by C. L. Taylor, E. Brinks, R. M. Grashuis, & E. D. Skillman (ApJS, 99,427(1995]), three objects were erroneously identified as being H I companion objects. The majority of the companion objects are unambiguously identified with optical counterparts and are considered to be genuine. For six objects we reported that no optical counterparts were present at about the 23 mag arcsec^-2^ level. Three of the six appear partially merged with their parent galaxies and will require VLA C-configuration observations to confirm their reality; the other three were well separated from the parent H II galaxy. Although these three objects met the same selection criteria as used to find the genuine companion objects, recent observations conducted to confirm their reality detected only one out of three: the companions UM 483A and UM 491B were not recovered and are taken to be false detections in the original observations, whereas the companion UM 422C was detected at the expected level and is confirmed as a genuine companion object. Further observations showed that UM 323A, for which we have no optical data, is a spurious detection as well. The spurious detections were caused by the presence of solar interference during the H I observations. Such interference is time- variable and frequency-dependent, and the measures described in the original paper were inadequate to entirely remove the effects of the interference in the instances of the false detections. As solar interference can be spatially correlated from channel to channel, the selection criteria, which assume random Gaussian noise, failed in the presence of the nonrandom residual interference. The residual interference mimicked a low-mass, H I-rich object as it would appear in observations of low spatial and velocity resolution. The process of companion candidate identification was designed to be followed up with confirmation observations, but it was only recently that we were given any VLA time to accomplish this. The new observations were carried out on 1995 June 6 and at night so as to avoid solar interference. In addition, the new data have ~50% lower noise, so any real objects ought to have been readily visible in the channel maps. The statistics of the companion frequency now change as follows in the light of the new observations. The frequency with which H II galaxies are observed to have nearby companions is 12/21 = 0.57, rather than the 14/21 originally reported. Using this new detection rate to recalculate the lower limit on the frequency of companion occurrence results in a value of ρ = 0.37. The corresponding upper limit is 0.76, but, as discussed in the paper, this is not nearly as strong a limit as is the lower limit, and we cannot rule out an upper limit of ρ = l. The lower and upper limits calculated from the original detection rate of 14/21 are 0.46 and 0.84, respectively. We present a new version of Figure 22 from the original paper, showing the histograms for the H I mass and total mass distributions of the companion object population. The histograms are not greatly changed as a result of omitting the three spurious objects. We should like to emphasize that most of the material presented in the original paper is reliable and that none of the discussion is significantly changed. We thank John Salzer, Renzo Sancisi, and Jacqueline van Gorkom for bringing to our attention the possibility of false detections caused by solar interference, and Miller Goss and Barty Clark for allocating time for the follow-up observations. Publication: The Astrophysical Journal Supplement Series Pub Date: January 1996 DOI: 10.1086/192256 Bibcode: 1996ApJS..102..189T full text sources ADS |

Joint ROSAT-Compton GRO observations of the X-ray bright Seyfert galaxy IC 4329A

view Abstract Citations (79) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Joint ROSAT--Compton GRO Observations of the X-Ray--bright Seyfert Galaxy IC 4329A Madejski, G. M. ; Zdziarski, A. A. ; Turner, T. J. ; Done, C. ; Mushotzky, R. F. ; Hartman, R. C. ; Gehrels, N. ; Connors, A. ; Fabian, A. C. ; Nandra, K. ; Celotti, A. ; Rees, M. J. ; Johnson, W. N. ; Grove, J. E. ; Starr, C. H. Abstract We report a simultaneous ROSAT and GRO observation of the X-ray-bright Seyfert galaxy IC 4329A. For the GRO OSSE detector, we also present the sum of the data for this and earlier observations. The overall spectrum is very well described as a power law with an energy spectral index of ~1 absorbed at low energies plus a strong Compton reflection component, typical for Seyfert 1 galaxies. The low energy absorption can be well described by a sum of a neutral column density of ~3 x 10^21^ cm^-2^, most of which is associated with the edge-on galactic disk of IC 4329A, plus an edgelike feature at ~700 eV; this feature implies either complex absorption (due to additional ionized material, or due to partial covering), or a soft excess. The data only weakly constrain the presence of a high-energy cutoff in the underlying power law; they are compatible with an exponential cutoff at any energy E_c_ ~> 100 keV. The relative steepness of the OSSE data, with the powerlaw energy index of 1.6 +/- 0.2, can be accounted for entirely by the contribution of the high-energy tail of the reflection component when E_c_ approaches {infinity}. (We find that the definite cutoff at an energy E_c_ ~ 130 keV suggested in the recently published analysis of the OSSE data for this object is due to a data reduction error.) Including nonsimultaneous Ginga observations with 2 keV fluxes matching well that of ROSAT gives us likely broadband X-ray/γ-ray spectra of the object from ~0.1 keV up to several hundred keV. Joint spectral analysis of the data sets from the three instruments gives results similar to those from ROSAT/OSSE only, except that the cutoff energy is now constrained to be at 250 keV <~ E_c_ <~ 1700 keV. The constraint on E_c_ markedly distinguishes this object from NGC 4151, where E_c_ was lower, ~50 keV; this has implications for emission models for AGNs as well as for their contribution to the X-ray background. We also report the ROSAT spectrum of the companion object to the Seyfert galaxy, the elliptical galaxy IC 4329 located ~3' away. Its spectrum is well described by an optically thin thermal plasma wi4th kT = 0.9 keV, with a 0.1-2 keV flux of 8 x 10^-13^ ergs cm^-2^ s^-1`^, corresponding to a luminosity of ~8 x 10^41^ ergs s^-1^. Publication: The Astrophysical Journal Pub Date: January 1995 DOI: 10.1086/175111 Bibcode: 1995ApJ...438..672M Keywords: Brightness; Elliptical Galaxies; Seyfert Galaxies; Stellar Spectra; X Rays; Gamma Ray Observatory; Gamma Rays; Ginga Satellite; Rosat Mission; Spectrum Analysis; Astrophysics; GAMMA RAYS: OBSERVATIONS; GALAXIES: INDIVIDUAL ALPHANUMERIC: IC 4329A; GALAXIES: INDIVIDUAL ALPHANUMERIC: IC 4329; GALAXIES: SEYFERT; X-RAYS: GALAXIES full text sources ADS | data products SIMBAD (4) NED (3) HEASARC (1)

A second companion of the millisecond pulsar 1620 – 26

MILLISECOND pulsars are usually found in binary systems. This is in keeping with the generally accepted model for the formation of such pulsars14 in which an old neutron star is spun up to high angular velocities by the accretion of matter from a companion star. The millisecond pulsar 1620 – 26 in the globular cluster M4 is no exception: timing measurements1,2 reveal the presence of a 0.3-solar-mass companion star (probably a white dwarf) with an orbital period of 191 days. But subsequent measurements of this pulsar have identified a small but significant deviation from the expected behaviour3,4, suggestive of an unusually large second derivative in the pulsar's rotation rate5. Here we examine several possible sources—both intrinsic and extrinsic—for this derivative, and we find that it is best explained by the presence of a second, weakly bound companion object moving in a wide orbit around the main binary system. The third body in this hierarchical system has an orbital period of ∼100 years and a mass approximately ten times that of Jupiter, and may have been captured during a recent collision with another stellar system6.

Constraints on the companion object to HD 114762

The paper presents high-precision radial velocity observations of the candidate planetary system HD 114762. The data obtained confirm Latham et al.'s (1989) of the binary nature of the system. The new orbital solution gives an eccentricity of 0.38 compared with the Latham et al. value of 0.25, but otherwise it agrees well with the discovery orbit. The mass function for the system implies a companion object with Mc sin i(orb) = 0.011 solar mass.

Implications of the Discovery of Sub-Millisecond Pulsar in SN1987A

From the observation of the sub-millisecond pulsar in SN1987A the following implications are obtained. 1) The stiff equation of state of neutron star matter, such as Mean Field, Tensor Interaction, Bethe and Johnson I are ruled out. 2) The pulsar has a possibility to collapse into a black hole by spin-down. 3) Although the sinusoidal modulation is explained by the existence of a 10-3M⊙ companion object, it seems hard to account for such an object in the scenario of the supernova explosion. We estimate the magnetic field, ellipticity and the mass of the neutron star and also the period of glitches.

Review of Speckle Observations of Supernova 1987A

AbstractSN 1987A is sufficiently close to allow a unique examination of the morphology of a supernova, using speckle interferometry. Several groups [Center for Astrophysics (CfA); Imperial College (IC); Mount Stromlo and Siding Spring Observatories/Anglo-Australian Observatory (M/A)] have reported optical speckle observations. At Hα, both CfA and M/A have determined the angular extent of the emission, and reasonable agreement is obtained. The speckle-derived values are consistent with those obtained from line profiles. IC has also succeeded in resolving the supernova at Hα. At wavelengths other than Hα, at early epochs, angular diameters obtained by CfA are larger than those derived from photometric and spectroscopic measurements, possibly due to scattering effects. At later epochs, the diameters exhibit little variation between the wavelengths examined. CfA reports significant asymmetry in the late epoch data.Several attempts have been made to re-observe (at optical wavelengths) the companion object, but none have succeeded. The nature of this phenomenon is still controversial, but the evidence indicates that the companion was real, with emission from dust apparently being the least problematic explanation. Support for this may lie in IR speckle observations (Haute Provence/Lyon) which, on about day 115, indicated the presence of one or more resolved components at an angular displacement comparable to that of the optical companion.

A galaxy at a redshift of 3.215 - Further studies of the PKS 1614+051 system

A narrow-emission-line companion of the quasar PKS 1614+051 was reported earlier as a probable galaxy at a redshift of 3.218, which would have made it by far the most distant galaxy known at the time. New radio and optical imaging, and optical and near-IR spectroscopy of the PKS 1614+051 system is reported here. It is argued that the data support and reinforce the original interpretation of the companion object as a mildly active galaxy, possibly a marginal Seyfert 2. The object has a detectable and marginally resolved optical continuum, but was not detected at radio wavelengths. The ionization state is low, and the emission lines are fairly narrow. The improved redshift for the companion, based on the Ly-alpha line alone, is 3.215 + or - 0.002. New Ly-alpha images show interesting morphology of extended emission-line gas, suggestive of a possible tidal interaction with the neighboring QSO. 24 references.

Further observations of the binary pulsar PSR 1913+16

view Abstract Citations (117) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Further observations of the binary pulsar PSR 1913+16. Taylor, J. H. ; Hulse, R. A. ; Fowler, L. A. ; Gullahorn, G. E. ; Rankin, J. M. Abstract Results are reported for more than a year's timing observations of the binary pulsar PSR 1913+16. Within the accuracy of the measurements, the pulse arrival times are exactly those expected from a clock of well-defined period moving in a Keplerian orbit with a constant rate of apsidal advance. The observations have yielded much-improved values for the parameters of the pulsar and its orbit, and are approaching the length of baseline needed to perform certain tests of gravitation theories. An upper limit of 60 microjansky is placed on periodically pulsed radio emission from the companion object. Publication: The Astrophysical Journal Pub Date: May 1976 DOI: 10.1086/182131 Bibcode: 1976ApJ...206L..53T Keywords: Binary Stars; Orbit Calculation; Periodic Variations; Pulsars; Companion Stars; Long Term Effects; Radio Emission; Stellar Mass; Astronomy full text sources ADS | data products SIMBAD (1)